The purpose of these studies was to study patients with abnormal host defense. In FY '91 studies focused mostly on patients with abnormal phagocytic cell function. Particular emphasis was given to patients with chronic granulomatous disease of childhood (CGD), who are the subject of intense study in the Laboratory of Host Defenses. Some of the clinical observations that were made this year included the following: Demonstration of invasive infection with Sarcinosporon inkin in a patient with CHD; demonstration that normal and abnormal neutrophils can cooperate to damage Aspergillus fumigatus, an observation with important clinical implications for use of white cell transfusions in CGD; demonstration that patients with CGD receiving long term prophylaxis with trimethoprim-sulfamethoxazole have reduced frequency of infection against catalase positive bacteria without increased incidence of fungal infection; completion of long term reviews of skeletal involvement by infection in CGD and anesthesia considerations in CGD; the clinical efficacy of in Gamma-interferon in CGD was demonstrated. We continue to monitor and expand these cohorts of patients as well as patients with leukocyte adhesion deficiency and the syndrome of hyperimmunoglobulin-E and recurrent infections.